updated downloaders to utilize nectar backend
chagend create and update to use importer config mixin
changed importer config generation to use mixin
caching sync and downloader instances and directly calling cancel instead of using the callback
fixed cli unit tests
changes to mimic current exception raising behavior and to make module more testable
moved downloader creation back into try block
updated importer unit tests
docstrings!
using cStringIO for performance
Merge pull request #67 from pulp/jconnor-nectar-importer

Jconnor nectar importer